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Turbomachinery getting started
This getting started guide provides a comprehensive introduction to thermal modeling for turbomachinery applications using Simcenter 3D Thermal Multiphysics.
Introducing boundary conditions
This topic explains the different types of boundary conditions used in turbomachinery simulations and how thermal, shared, and structural conditions are applied through simulation objects, constraints, and loads to represent multiphysics behavior.
Convection boundary conditions
This topic explains what thermal boundary conditions you can use for convection.
Method 1: Surface-based convection boundary conditions
Boundary condition ID in expressions
This topic explains how boundary condition IDs are assigned and modified for streams, voids, convecting zones, and duct labels, including how to renumber or offset IDs for use in expressions.

Knowledge base articles
Knowledge base articles provide concise, practical guidance for solving thermal, flow, multiphysics, space systems, and turbomachinery modeling challenges in Simcenter 3D.
Space thermal getting started
This getting started guide provides a comprehensive introduction to space thermal modeling using Simcenter 3D Space Systems Thermal (SST).
Turbomachinery getting started
This getting started guide provides a comprehensive introduction to thermal modeling for turbomachinery applications using Simcenter 3D Thermal Multiphysics.
- Getting started with turbomachinery in Simcenter 3D
- Fundamentals of turbomachinery systems
  This topic introduces turbomachinery and explains how gas turbines convert working-fluid energy into mechanical energy or thrust. You will learn how turbomachines are classified, how the Brayton cycle describes gas turbine operation, and how the main gas turbine sections, components, and cooling systems support safe and efficient performance.
- Gas turbine design disciplines and data exchange
  This topic introduces the main engineering disciplines involved in gas turbine design and explains how they exchange data throughout the development process. You will learn how different teams collaborate, what data they produce, and how iterative workflows drive the final engine design.
- Introducing Whole Engine Model (WEM)
  This topic introduces the WEM and explains its role in gas turbine design. You will learn how WEM captures the thermal and structural behavior of the engine, what inputs it requires, and how it supports clearance and mechanical integrity assessments.
- Introducing the user interface
  This topic covers the user interface (UI) in Simcenter 3D Thermal Multiphysics. You will learn how to navigate the modeling environment and how to efficiently use the available tools, menus, and commands to build, set up, and review your models.
- Preparing geometry for WEM
  This topic explains why geometry preparation is critical for WEM analysis. You will learn how to simplify 3D CAD geometry into efficient 2D or hybrid models and how to prepare geometry for meshing and simulation in Simcenter 3D.
- Meshing strategy
  This topic explains how to create finite element models for WEM by combining multiple mesh types and abstraction levels.
- Managing parts and assemblies
  This topic explains how to manage parts and assemblies in WEM using associative geometry, collaborative simulation capability, and integration of submodels into a full engine simulation.
- Condition sequences
  This topic explains how condition sequences define and manage engine operating conditions over a mission cycle in WEM.
- Introducing boundary conditions
  This topic explains the different types of boundary conditions used in turbomachinery simulations and how thermal, shared, and structural conditions are applied through simulation objects, constraints, and loads to represent multiphysics behavior.
  - Thermal coupling
    This topic explains how to model heat transfer between components that are not directly connected through the mesh in WEM simulations.
  - Convection boundary conditions
    This topic explains what thermal boundary conditions you can use for convection.
    - Method 1: Surface-based convection boundary conditions
      - Introducing surface-based convection boundary conditions
        This topic explains how to model surface-based convection using Thermal Streams, Thermal Voids, and Thermal Convective Zones, and how to apply them to represent different flow behaviors and heat transfer mechanisms.
      - Defining thermal streams
        This topic explains how to define and use Thermal Streams to model convective heat transfer, including setup, required inputs, stream types, governing equations, and advanced options for accurate modeling.
      - Connecting thermal streams
        This topic explains how to connect thermal streams.
      - Defining thermal voids
        This topic explains how to define and use Thermal Void to model enclosed fluid regions with simplified thermal behavior, including setup, governing energy equation, required properties, and options to represent heat transfer, capacitance, and interactions with surrounding solids and streams.
      - Defining thermal convecting zones
        This topic explains how to define thermal convecting zones to model heat transfer to a fluid at a known temperature, acting as a fixed-temperature convective sink.
      - Boundary condition ID in expressions
        This topic explains how boundary condition IDs are assigned and modified for streams, voids, convecting zones, and duct labels, including how to renumber or offset IDs for use in expressions.
    - Method 2: Coupled 1D duct fluid network
    - Comparing two methods
      This topic compares thermal streams and 1D duct networks, as well as voids and duct-node approaches, highlighting their differences in workflow, control, and suitability for modeling convective heat transfer in turbomachinery.
    - Modeling mixed flow from two ducts into the thermal stream
      This topic explains how to model mixing of flows from multiple ducts into a thermal stream, including methods using expressions, mock streams, the MIX function, and thermal stream junctions.
    - Relative temperature effects
      This topic explains how to account for total temperature effects in turbomachinery simulations, particularly in systems with rotating and stationary components.
  - Fields, expressions and plugins
    This topic explains how to define boundary condition inputs in Simcenter 3D using fields, expressions, and plugin functions. These tools allow you to model complex, time- and space-dependent behavior efficiently.
  - Radiation modeling
    This lesson explains the two Radiation simulation object types and how each defines radiative enclosures and affects radiation calculation efficiency.
  - Cyclic Symmetry
    This topic explains how to use Cyclic Symmetry in turbomachinery thermal models.
- Solving a model
  This topic explains how to configure thermal-solver settings in WEM, including convergence criteria, discretization methods, integration methods, and axisymmetric-segment control for accurate and efficient thermal analyses.
- Post-processing results
  This lesson introduces post-processing commands to help you review and evaluate simulation outcomes using visualization and data analysis.
- Mechanical integrity
  This topic explains how thermal results from WEM are mapped to detailed component models for structural and mechanical integrity analyses.
- Blade cooling
  This topic explains why blade cooling is critical in gas turbines and how advanced cooling technologies allow turbine components to operate at temperatures above material limits.
- Troubleshooting the model
  This topic explains how to verify FEM quality, material definitions, mesh integrity, and element properties before solving a thermal model.

Boundary condition ID in expressions

This topic explains how boundary condition IDs are assigned and modified for streams, voids, convecting zones, and duct labels, including how to renumber or offset IDs for use in expressions.

This lesson may include hands-on exercises. Review the Discussion section for background information or click the button to proceed to the practical section.

Discussion

When you create streams, voids, and convecting zones, and duct labels, the software assigns a numerical ID to the boundary condition. These IDs are used by thermal-flow functions, such as STO, SMO, and others, to reference boundary-condition results within expressions.

When you change the boundary condition ID number, the software automatically updates all the formulas for expressions that contain the numerical ID to reflect the new ID number.

For example, suppose a model contains a stream whose numerical ID is 23 and an expression whose formula contains STO(23). If you change the numerical ID of the stream to 35, the software automatically changes STO(23) to STO(35) in the formula for the expression.

To change the numerical ID of these boundary conditions, you can:

Edit the numerical ID in the dialog box for the boundary condition.
Use the Renumber and Offset options for changing ID numbers.

The following examples show how the numbering of the streams is changed depending on selected options.

If you select the Renumber option, and enter 11 in the From box, the stream ID numbers change as follows:

Stream 3 → Stream 11
Stream 1 → Stream 12
Stream 4 → Stream 13
Stream 2 → Stream 14

If you select the Offset option, and enter 11 in the By box, the stream ID numbers change as follows:

Stream 3 → Stream 14
Stream 1 → Stream 12
Stream 4 → Stream 15
Stream 2 → Stream 13

Hands-on material

To gain experience with the topics discussed here, complete the following:

Define convection boundary conditions at 2D interfaces